As public health officials struggle to contain a series of viral outbreaks this winter, many people are reaching for bottles of hand sanitizer.

Studies show that alcohol-based sanitizers, particularly those with 60 percent ethanol or more, can reduce microbial counts on contaminated hands and reduce the spread of some strains of the flu. But against norovirus, the severe gastrointestinal illness gripping many parts of the country, they may be useless.

Some viruses, like influenza, are coated in lipids, "envelopes" that alcohol can rupture. But non-enveloped viruses, like norovirus, are generally not affected.

Bleach is effective against norovirus and can be used to decontaminate countertops and surfaces. And for people, the best strategy may be washing hands with plain old soap and water.

Younger women who ate at least three servings per week of strawberries or blueberries reduced their likelihood of suffering a heart attack by one-third compared with their sisters who incorporated fewer of the colorful berries into their diet, a new study says.

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Researchers suggested that a group of dietary flavenoids called anthocyanins, which give blueberries and strawberries their jewel-like colors, may be responsible for the health benefits seen in the study's large sample of subjects.

Anthocyanins are known to dilate arteries and counter the buildup of plaque that causes atherosclerosis.

The study, published in the American Heart Association's journal, Circulation, found the subjects who ate the most strawberries and blueberries, three or more servings weekly, were 32 percent less likely to be among the group who suffered early heart attack than were women who ate fewer berries — even women whose diets were otherwise rich in fruits and vegetables.

About 27 million people in the United States have osteoarthritis, an incurable condition with few effective treatments beyond pain control. Some observational evidence suggests that vitamin D supplements might slow progression of the disease.

But a two-year randomized placebo-controlled study found that vitamin D did not reduce knee pain or restore cartilage.

In an article published in The Journal of the American Medical Association last week, researchers described a study of 146 men and women with painful knee arthritis who were randomly assigned to take vitamin D supplements or placebos. Vitamin D was given in quantities sufficient to raise blood levels to 36 nanograms per milliliter, a level considered sufficient for good health.

Knee pain decreased slightly in both groups, but there were no differences in the amount of cartilage lost, bone mineral density or joint deterioration as measured by X-rays and MRI scans.